1. Field of the Invention
The invention generally relates to distributed optical network management systems and methods. The invention more particularly relates to methods and systems that perform distributed optical network management of faults and alarms.
2. Description of Related Art
Optical communication systems are a substantial and fast growing constituent of communication networks. The expression “optical communication system,” as used herein, relates to any system which uses optical signals to convey information across an optical waveguiding medium, for example, an optical fiber. Such optical systems include but are not limited to telecommunication systems, cable television systems, and local area networks (LANs). (Optical systems are described in Gowar, Ed. Optical Communication Systems, (Prentice Hall, New York) c. 1993, the disclosure of which is incorporated herein by reference.)
Currently, the majority of optical communication systems are configured to carry an optical channel of a single wavelength over one or more optical waveguides. To convey information from multiple sources, time-division multiplexing (TDM) is frequently employed. In TDM, a particular time slot is assigned to each signal source with the complete signal constructed from portions of the signal collected from each time slot. While this is a useful technique for carrying plural information sources on a single channel, its capacity is limited by fiber dispersion and the need to generate high peak power pulses.
While the need for communication services increases, the current capacity of existing waveguiding media is limited. Although capacity may be expanded (e.g., by laying more fiber optic cables), the cost of such expansion is prohibitive. Consequently, there exists a need for a cost-effective way to increase the capacity of existing optical waveguides.
Wavelength division multiplexing (WDM) is being explored as an approach for increasing the capacity of existing fiber optic networks. WDM systems typically include a plurality of transmitters, each respectively transmitting signals on a designated channel or wavelength. The transmitters are typically housed in a first terminal located at one end of a fiber. The first terminal combines the channels and transmits them on the fiber to a second terminal coupled to an opposite end of the fiber. The channels are then separated and supplied to respective receivers within the second terminal.
The WDM system described in the previous paragraph can be perceived as a point-to-point connection with multiple signals carried from one terminal to the other. However, it is frequently advantageous to add and drop channels at various locations between the two terminals. Accordingly, other network elements, such as add/drop modules are often provided along the fiber in order to inject and/or remove channels from the fiber. Moreover, if the fiber extends over long distances, it is necessary to segment the fiber into sections with each fiber section being coupled to another by an additional network element that amplifies the signal (e.g., an erbium doped fiber amplifier).
In addition to the information bearing channels described above, Condict '115 utilizes a service channel at a wavelength different than the information bearing channels and carrying diagnostic and span topology information can also be transmitted through each span. Information associated with a span may be coupled via Ethernet connections to an internet protocol (IP) router. This IP router passes the information via the Internet to additional IP routers. A local area network (LAN) then transmits the information between the IP routers and to the network monitoring equipment. Finally, information associated with a span is similarly passed to network monitoring equipment through Ethernet links and an IP router.
The Condict '115 patent ensures proper operation of the WDM system by monitoring each network element. In the event of a failure, such as a fiber break, the communication system maintains its ability to monitor each network element by using, for example, a service channel separate from the main optical communication channel. Moreover, the communication system automatically responds to a fault by having each network element identify itself and report information about its operating status.
The Condict '115 patent further includes an optical communication path and a plurality of network elements disposed along the optical communication path. A first network element coupled to the optical communication path includes a first processor and a first optical component. The status of the first optical component is monitored by the first processor. The first processor generates a first electrical signal in accordance with the status of the first optical component. The first network element also includes a service channel transmitter coupled to the first processor and emits a second optical signal to the optical communication path at a second wavelength different than the first plurality of wavelengths in response to the first electrical signal. The second optical signal being modulated in accordance with the second electrical signal. A second network element is coupled to the optical communication path and includes a second processor, a second optical component coupled to the second processor and a service channel receiver coupled to the first processor and to the optical communication path. The receiver senses the second optical signal. The service channel receiver outputs a second electrical signal to the second processor in response to the second optical signal. The second processor controls the second optical component in response to the second electrical signal.
The Condict '115 patent span management systems and methods manage a span of an optical network in which each network element exchanges identification and status information for performing various monitoring and control functions in the optical network.